Railroad rails are commonly bolted together with a pair of fishplates or joint bars in a manner allowing considerable vertical movement of the rails relative to each other. As each train wheel leaves one rail, it depresses that rail relative to the other and then batters the other rail. After a time, it becomes necessary to repair the battered end of the rail or to replace the rail.
This problem has been partially overcome by welding the rails together, but welded track involves additional problems arising from huge expansion and contraction forces in long sections of welded track with changes in temperature. Also, it is expensive to replace individual rails of welded track. At electrically insulated joints of welded track, the same problem of rail-end batter is involved.
In an effort to reduce rail end batter, some railroads have been experimenting with adhesively bonded rail joints in order to inhibit vertical movement of the rail ends with respect to each other. However, such adhesively bonded rail joints have created a new set of problems. Adhesives which have thus far been used cure rather slowly and require that the line be kept out of service for unduly long periods of time. Then the joint bars become so strongly bonded to the rail that the joint is difficult to dismantle if maintenance is required.